Non-shortning pin system

ABSTRACT

The invention is a zero insertion force printed circuit board edge connector that ensures electrical connection under a worst-case accumulation of mechanical tolerances while precluding the short circuiting of connector contact pins in the absence of a board within the connector. The contact pins of the connector are formed so that the contact regions of the contact pins lie in at least two horizontal planes. The longer pins located on one side of the connector are located opposite the shorter pins on the other side of the connector. When the connector is actuated in the absence of a printed circuit board, the short pins will move under the opposing long pins but the pins will not short circuit. During actuation, the pins will move more than half way across the connector opening thereby guaranteeing connection to any card regardless of dimensional tolerance or of card position within the connector opening.

.Iadd.This is a reissue of U.S. Pat. No. 4,598,966 issued July 8, 1986which application was Ser. No. 471,955 filed Mar. 3, 1983. .Iaddend.

DESCRIPTION

1. Field of the Invention

The invention relates to a non-shorting pin configuration used in a zeroinsertion force (ZIF) type printed circuit board edge connector.

2. Background Art

It is well known in the art that substantial force is required to inserta printed circuit board into an other-than-ZIF mating edge connector dueto the wiping engagement between the electrical contact pads on theboard and the contact regions of the pins or springs in the matingconnector. As the number of contacts increases, the force required toeffect insertion also increases and will eventually reach a point wherethe force required will be excessive for practical use. Also, repeatedinsertion and extraction of a board into and from a corresponding matingconnector will cause repeated wipings to occur between the contact padsand the contact springs and may result in excessive wear to the contactpads.

A common solution to this problem is the zero insertion force (ZIF) typeconnector. In these connectors, the contact pins located in theconnector are movable between two positions. In the first position, thepins are retracted from the board insertion path thereby allowing theunobstructed and low force insertion of the printed circuit board intothe connector. In the second position, the contact pins are moved by anactuator into engaging contact with the contact pads of the board.

When designing a zero insertion force connector, mechanical tolerancesof the printed circuit board and of the mating connector must beconsidered. These mechanical tolerances stem from unavoidablemanufacturing deviations from piece to piece and from lot to lot as wellas variations in mechanical dimensions due to environmental operatingconditions. A prudent design of a zero insertion force connectorintended for large volume production will ensure that every printedcircuit board can mate with every connector under a worst-caseaccumulation of mechanical tolerances. Further, previous connectors haveoppositely aligned contact pins which, under a worst-case design willcause the contact pins of a dimensionally nominal connector to touch theopposite facing pins when the pins are actuated in the absence of aprinted circuit board in the connector. This invention avoids suchproblems.

In a modular or expandable system using a plurality of zero insertionforce connectors, often several of the connectors are vacant, i.e.,without printed circuit boards. Esthetics or other constraints oftenrequire these vacant connectors to be in the actuated or closed state.If the opposite facing contact pins of the vacant and closed connectorstouch each other thereby producing electrical short circuits, damage tothe remaining electrical circuitry may result or erroneous signals maybe generated.

It is therefore desirable to provide a zero insertion force typeelectrical connector that will not cause opposite facing contact pins tocontact and short circuit when the pins are actuated in the absence of aprinted circuit board within the connector. This connector must alsomaintain a conservative worst-case design philosophy to ensurecompatibility between any board/connector combination.

SUMMARY OF THE INVENTION

The invention as herein described and claimed will resolve the drawbacksof the prior art. It solves the problem of providing a zero insertionforce printed circuit board edge connector that will ensure electricalconnection under a worst-case accumulation of mechanical toleranceswhile precluding the short circuiting of connector contact pins when theconnector is actuated in the absence of a board within the connector.The invention includes a unique connector contact pin configuration anda unique contact pad pattern for the edge of the mating printed circuitboard.

Self-based, spring-like contact pins of the connector are formed so thatthe contact regions of the contact pins lie in at least two horizontalplanes. The longer pins located on one side of the connector are locatedopposite the shorter pins on the other side of the connector. When theconnector is actuated in the absence of a printed circuit board, theshort pins will move under the opposing long pins but the pins will notcontact or short circuit. During actuation, contact regions of the pinswill move more than half way across the connector opening, therebyguaranteeing wiping contact with and electrical connection to any cardregardless of dimensional tolerance or of card position within theconnector opening.

The formed pins will mate with a unique pattern of contact pads disposedalong at least one edge of the printed circuit board. The rows ofcontact pads are offset and slightly interleaved in order to minimizethe board area required for electrical connections while maintaining ahigh probability of contact.

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of the preferred embodiments of the invention, asillustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a ZIF type connector in partial cross section showinga row of electrical contact pins and a printed circuit board with a tworow contact pad pattern.

FIG. 2 shows a two row electrical contact pad pattern and a three rowelectrical contact pad pattern disposed on the edge of a printed circuitboard.

FIG. 3A shows a cross section of a connector like that in FIG. 1illustrating the actuation sequence of a pair of opposing contact pinswith certain other pins removed for clarity.

FIG. 3B shows a view of the connector of FIG. 3A taken through section3B--3B.

FIG. 4 shows a ZIF type connector in partial cross section showing a rowof electrical contact pins and a printed circuit board with a three rowelectrical contact pad pattern.

DESCRIPTION OF AT LEAST ONE WAY OF CARRYING OUT THE INVENTION

Referring to FIG. 1, mother board 101 has mounted thereon a connector102 of the zero insertion force (ZIF) type. Connector 102 is shown inpartial cross-section to better illustrate the internal actuatormechanism. ZIF connector 102 is used to make electrical contact betweenprinted circuit board unit 103 and mother board 101. Printed circuitboard unit 103 includes a printed circuit board 104 with electricalcomponents 105 mounted thereon. Although only one electrical component105 is shown in FIG. 1, it will be understood that more than onecomponent 105 can be mounted on printed circuit board 104. Circuittraces 106 are used to electrically connect components 105 with eachother and with electrical contact pads 107 disposed in rows along theedge of printed circuit board 104.

Electrical contact pads 107 are shown in FIG. 1 arranged in two rowsnear the edge of printed circuit board 104. Long electrical contact pins108 have contact regions 109 for contacting pads 107 located in the rowfarthest from the edge of printed circuit board 104. Short electricalcontact pins 110 have contact regions 111 for contacting pads 107located in the row nearest to the edge of printed circuit board 104.

Actuating handle 112 of connector 102 pivots about hinge pin 113 andmoves linear cam 114 longitudinally of connector 102. When handle 112pivots in a counterclockwise direction, linear cam 114 moves to theright parallel to the longitudinal dimension of connector 102. Whenhandle 112 pivots in a clockwise direction, linear cam 114 moves to theleft.

Linear cam 114 includes cam lobes 115 which ride on cam followers 116during the motion of linear cam 114. The interaction between camfollowers 116 and cam lobes 115 during the motion of linear cam 114cause linear cam 114 to move perpendicular with the surface of motherboard 101 thereby moving housing 117 in the same direction.

Housing 117 is made of an electrically insulating material and is formedwith an elongated opening 122 at the top thereof. Printed circuit board103 is received into housing 117 through elongated opening 122 along aboard insertion path. The board insertion path can be generallydescribed as a vertical plane passing through elongated opening 122 andoriented substantially parallel with the longitudinal dimension ofelongated opening 122.

Housing 117 contains upper inclined surfaces 118 that cooperate withlong contact pins 108 and lower inclined surfaces 119 that cooperatewith short contact pins 110. As housing 117 is urged by linear cam 114to move away from mother board 101, inclined surfaces 118 and 119 moveelectrical contact pins 108 and 110, respectively, toward electricalcontact pads 107 located on printed circuit board 104. Electricalcontact pins 108 and 110 are self-biased to assume a normal positionretracted from printed circuit board 104 and as housing 117 moves towardmother board 101, electrical contact pins 108 and 110 move away fromprinted circuit board 104. In this manner, electrical contact pins 108and 110 will move into and out of contact with pads 107 as handle 112 ispivoted.

Electrical contact pins 108 and 110 extend through base portion 120 ofZIF connector 102 and through vias 121 in mother board 101. Vias 121will typically be connected to circuit traces (not shown) disposed onthe surface of mother board 101. These traces will serve to makeelectrical connections between pins 108 and 110 and electronic circuitrylocated elsewhere on mother board 101.

Another row of contact pins within housing 117, similar to pins 108 and110, is located on the hidden side of printed circuit board unit 103 inFIG. 1. This other row is also moved into and out of contact withelectrical contact pads located along the edge of the hidden surface ofprinted circuit board 104 as handle 112 is pivoted. The configuration ofopposing pin rows will be detailed in FIG. 3.

Here it should be noted that the particular actuator mechanism in ZIFconnector 102, used to urge pins 108 and 110 toward printed circuitboard 104, herein described and illustrated in FIG. 1, is but one ofseveral possible mechanisms that are well known to one skilled in theart. The presentation of this particular actuation mechanism is forillustrative purposes only and should not be construed to limit thescope of the claimed invention.

FIG. 2 illustrates an offset and interleaved electrical contact padpattern disposed along the edge of a printed circuit board 200 accordingto this invention.

The pad pattern is based on the understanding that the ideal target areafor a contact pin to touch and wipe a contact pad is an elliptical area201. This elliptical area 201 is derived by statistical mechanicaltolerance analysis techniques well known to a skilled artisan.

Area 201 is calculated by consideration of mechanical dimensionaltolerances including tolerances associated with contact pin length andwidth as well as tolerances associated with printed circuit board 200dimensions and horizontal and vertical position within a matingconnector. The border (dashed line) of elliptical area 201 represents acontour of equal probability of contact between a contact pin and thesurface of printed circuit board 200. Area 201 represents the area ofhigh probability of contact while the area outside of area 201represents the area of low probability of contact. A particularelliptical area 201 is chosen according to the requirements of theparticular printed circuit board application. If a small elliptical area201 is chosen, electrical contact pads 202 can be closely spaced but atthe cost of reducing the probability of electrical contact. If a largearea 201 is chosen, the probability of electrical contact will increasebut electrical contact pads 202 will be required to be spaced furtherapart.

A two row pad pattern is shown in solid lines in FIG. 2. Row 203 islocated nearest the edge of printed circuit board 200 and row 204 islocated farthest from the edge. Each individual contact pad 202 and 206encloses a single elliptical area 201. The edges of pads 202 and 206 arestraight lines in order to facilitate the layout of printed circuitboard 200.

Pads 206 of row 204 are slightly interleaved with and offset withrespect to pads 202 of row 203. Offsetting and interleaving the padpatterns in this manner will allow row 204 to be located closer to theedge of printed circuit board 200 thereby reducing the area required forelectrical connections while preserving the remaining interior area ofprinted circuit board 200 for the mounting of electrical components.

A third row 207 of electrical contact pads 208 can be added as shown bydashed lines in FIG. 2. In order to accommodate row 207, pads 206 mustbe modified to the diamond-shape shown in dashed lines. In a three rowpad pattern each individual pad (202, 206, 208) contains an ellipticalarea 201 of high probability of contact.

The pads 208 of third row 207 are slightly interleaved and offset withrespect to pads 206 of row 204. Once again, this allows third row 207 tobe located closer to the edge of printing circuit board 200 therebypreserving the remaining interior area of printed circuit board 200 forthe mounting of electrical components.

Any number of rows of electrical contact pads can be added in the samemanner as the addition of row 207 herein described. The favorableoverall effect of this new pad pattern is to minimize the printedcircuit board area required for electrical connection while maintaininga high probability of making contact between contact pins and contactpads.

Referring to FIG. 3, a ZIF connector 300 mounted to mother board 301, isshown in cross-section and is similar to ZIF connector 102 shown inFIG. 1. In FIG. 3, the printed circuit board unit is removed fromconnector 300 and short contact pin 302 and long contact pin 303 areshown opposite each other. ZIF connector 300 is shown in the actuatedposition as linear cams 304 urge housing 305 away from mother board 301.Inclined surfaces 306 and 307, contained within housing 305, force shortcontact pin 302 and long contact pin 303, respectively, toward thecenter line 308 of connector 300. Center line 308 is substantiallycoplanar with the board insertion path described during the discussionof FIG. 1.

In FIG. 3A, contact regions 309 and 310 of contact pins 302 and 303,respectively, have passed through center line 308 but as shown in FIG.3A, they do not touch one another. Contact region 309 of short pin 302is under contact region 310 of long contact pin 303.

Here it should be noted that not all of the contact regions of all ofthe opposed contact pin pairs of every connector must pass throughcenter line 308. The mechanical tolerances mentioned earlier mayaccumulate such that none or only some of the contact regions passthrough center line 308 in any one given connector of a production lot.However, in another given connector, mechanical tolerances mayaccumulate such that all contact regions of all opposed contact pinpairs pass through center line 308. The offset pin configuration hereindescribed and claimed will guarantee that no opposed pins will touch andshort circuit in any connecter of the production lot.

Contact pins 302' and 303' show the positions of pins 302 and 303,respectively, when they are in the self-biased, retracted positionthereby clearing center line 308 allowing a printed circuit board unitto enter connector 300. Pins 302 and 303 assume the retracted positionsof 302' and 303' when linear cam 304 is moved thereby allowing housing305 to move closer to mother board 301.

Inclined surfaces 311 and 312 are contained within housing 305 and serveto move the set of contact pins adjacent pins 302 and 303. This set ofadjacent pins is not shown in FIG. 3A in order to eschew obfuscation.

FIG. 3B is a view taken through section 3B--3B of FIG. 3A. In FIG. 3B,long pin 313 is shown adjacent short pin 302. Inclined surface 311 isattached to housing 305 and serves to move long pin 313 when housing 305is moved by linear cam 304. Long pin 313 has a contact region 314 thatlies substantially in a first horizontal plane with contact region 310of long pin 308 shown in FIG. 3A. The contact regions of all remaininglong contact pins in ZIF connector 300 also substantially lie in thisfirst horizontal plane.

Adjacent long pin 313 in FIG. 3B is short pin 315 with cooperatinginclined surface 316 attached to housing 305. Contact region 317 ofshort pin 315 substantially lies in a second horizontal plane withcontact region 309 of short pin 302. The contact regions of allremaining short pins in ZIF connector 300 also substantially lie in thissecond horizontal plane.

The preferred configuration of alternating long pins and short pinswithin a single row is shown in FIG. 3B and also in FIG. 1. In FIG. 3,contact regions are shown to lie in only two horizontal planes becausethe connector illustrated in FIG. 3 is disposed to contact and wipe atwo row pad pattern (e.g., rows 203 and 204 of FIG. 2). In order tocontact and wipe a three row pad pattern (e.g., rows 203, 204, and 207of FIG. 2) the contact regions of the contact pins would liesubstantially in three different horizontal planes and the contact pinswould be of three different lengths. This is illustrated in FIG. 4.

In general, the contact regions of the contact pins will substantiallylie in a number of horizontal planes equal to the number of contact padrows on the corresponding mating printed circuit board. Also, due to thealternating pin lengths hereinbefore described, the contact regions ofthe pins will be distributed among these horizontal planes insubstantially equal proportion.

FIG. 4 shows a ZIF connector 400 in partial cross section with acorresponding printed circuit board 401. ZIF connector 400 includes anactuator mechanism comprising the following elements: handle 402, linearcam 403 with cam lobes 404, cam followers 405, and housing 406. Thecomponents of this actuator mechanism cooperate in the same manner asthe actuator mechanism of FIG. 1 to move housing 406 upward as handle402 pivots counterclockwise. Once again, the illustration of thisparticular actuator mechanism should not be construed to delimit theinvention in any manner.

Housing 406 contains inclined surfaces 407, 408 and 409 that cooperatewith short pins 410, mid-length pins 411, and long pins 412,respectively. As housing 406 moves upward, in response to thecounterclockwise pivoting of handle 402, inclined surfaces 407, 408, and409 move pins 410, 411 and 412, respectively, toward printed circuitboard 401 when printed circuit board 401 is inserted into ZIF connector400.

Long pins 412 are disposed to contact and wipe electrical contact padsin row 413 located along the edge of printed circuit board 401. Midlength pins 411 are disposed to contact and wipe electrical contact padsin row 414 located along the edge of printed circuit board 401. Shortpins 410 are disposed to contact and wipe electrical contact pads in row415 located along the edge of printed circuit board 401.

Once again, the contact regions of the contact pins pass through theplanar board insertion path when connector 400 is actuated in theabsence of printed circuit board 401 within connector 400. In order toavoid contact between opposing pins, a mid length pin is locatedopposite a short pin and a long pin so that the contact regionassociated with the mid length pin will pass over the top of the contactregion associated with the opposing short pin, and will pass under thecontact region associated with the opposing long pin. In this manner,the contact regions of opposing pins will not touch and short circuitwhen ZIF connector 400 is actuated in the absence of printed circuitboard 401 within connector 400.

This scheme of opposing contacts can be expanded to encompass a ZIFconnector capable of contacting a printed circuit board with any numberof rows of contact pads disposed along an edge thereof. Short circuitingof opposing contact pins is precluded by ensuring that each contact pinin the connector is never opposite a contact pin of equal length havinga contact region in the same horizontal plane.

It will be understood that the preferred embodiments herein presentedare for illustrative purposes, and, as such, will now be construed toplace limitations on the invention. Those skilled in the art willunderstand that changes in the form and detail of the preferredembodiments recited may be made without departing from the spirit andscope of the invention.

I claim:
 1. In a zero insertion force type electrical connector for receiving an electrical component type having a plurality of rows of contact pads disposed on opposite sides of a flat surface thereof, said contact pads including a first row of pads on a given side of said electrical component offset and interleaved with respect to pads in an adjacent second row and on the same side of said electrical component, insulating gaps separating said pads in said first row narrower than the width of the contacting region of said pads in said second row to provide a high density contact pad pattern, an electrical connector comprising:a housing of electrically insulating material having a base and two side walls together defining an elongated opening at the top of said housing for receiving therein said electrical component; upper inclined surfaces on the inside of each side wall of said housing facing the elongated opening in said housing; lower inclined surfaces on the inside of each side wall of said housing facing the elongated opening in said housing; a first row of spring-like contact pins having alternating long and short pins on one side of said elongated opening; a second row of spring-like contact pins having alternating long and short pins on the other side of said elongated opening in staggered relation to said first row of contact pins wherein the long pins of said first row are opposite said short pins of said second row and the short pins of said first row are opposite said long pins of said second row; contact regions of said short contact pins for contacting the interleaved contact pads located in the row of pads nearest to the edge of the electrical component; contact regions of said long contact pins for contacting the interleaved contact pads located in the row of pads farthest from the edge of the electrical component; actuating means for moving said .Iadd.side walls of said .Iaddend.housing .Iadd.away from said base .Iaddend.in a vertical plane wherein said lower inclined surfaces urge said short contact pins and said upper inclined surfaces urge said long contact pins in a direction toward the center of said elongated opening; said contact regions of said short pins passing through said centerline of said elongated opening wherein the contact region of each short pin is below said contact region of said opposite long pin thereby precluding opposite facing contact pins from contacting and short circuiting when the contact pins are actuated in the absence of an electrical component within the connector; and said contact regions of said long pins passing through said centerline of said elongated opening wherein the contact region of each long pin is above said contact region of said opposite short pin thereby precluding opposite facing contact pins from contacting and short circuiting when the contact pins are actuated in the absence of an electrical component within the connector.[.;.]. .Iadd.. .Iaddend. .[.upon insertion of an electrical component vertically into said elongated opening of said housing through a vertical plane oriented substantially parallel with the longitudinal dimension of said elongated opening, electrical connection is completed..]. .Iadd.
 2. A zero insertion force type electrical connector for receiving an electrical component having a plurality of rows of contact pads disposed on opposite sides of a flat surface thereof comprising:a housing of electrically insulating material having a base and two side walls together defining an elongated opening at one end of said housing for receiving therein said electrical component; first inclined surfaces on the inside of each side wall of said housing facing the elongated opening in said housing; second inclined surfaces on the inside of each side wall of said housing facing the elongated opening in said housing and further removed from said opening than said first inclined surfaces; a first row of spring-like contact pins having alternating long and short pins on one side of said elongated opening; a second row of spring-like contact pins having alternating long and short pins on the other side of said elongated opening in staggered relation to said first row of contact pins wherein the long pins of said first row are opposite said short pins of said second row and the short pins of said first row are opposite said long pins of said second row; actuating means for moving said side walls of said housing away from said base wherein said second inclined surfaces urge said short contact pins and said first inclined surfaces urge said long contact pins in a direction toward the center of said elongated opening; said contact regions of said short pins passing through said centerline of said elongated opening wherein the contact region of each short pin is under said contact region of said opposite long pin thereby precluding opposite facing contact pins from contacting and short circuiting when the contact pins are actuated in the absence of an electrical component within the connector; and said contact regions of said long pins passing through said centerline of said elongated opening wherein the contact region of each long pin is over said contact region of said opposite short pin thereby precluding opposite facing contact pins from contacting and short circuiting when the contact pins are actuated in the absence of an electrical component within the connector. .Iaddend. .Iadd.
 3. A zero insertion force, card edge connector, adapted to engage the conductive traces on a card inserted in a card receiving slot in the connector, comprising:a. an elongated first housing with a base; b. an elongated second housing positioned over the first housing having a longitudinally extending card receiving slot and cam surfaces facing the slot with said cam surfaces being located at more than one level position; c. cam means positioned between the first and second housings for moving the second housing away from said first housing; and d. contact elements arranged in a pair of rows and retained in the base in the first housing, each element having a cantilevered portion extending into the second housing between the slot and cam surfaces with a contact surface facing the slot for engagement with a conductive trace on a card inserted in the slot, and a convex surface positioned adjacent a cam surface on the second housing for engagement with the cam surface during movement of the second housing away from said first housing to move the contact surface into engagement with a trace on a card positioned in the slot,the cantilevered portions of the elements on each side of the slot being longitudinally spaced from each other, the elements being arranged in opposing pairs whose contact surfaces face one another across the slot, the contact surfaces on adjacent elements along each side of the slot being located at different positions, and the facing contact surfaces on elements located on opposite sides of the slot located at different level positions and further with all elements having contact surfaces at each level position having their associated cam surfaces located at one level position. .Iaddend. 